System and method for controlling time critical operations in a control system for an optical disc drive

ABSTRACT

A system, method, and apparatus for coordinating tasks in a control system for an optical disc drive for optical media with a pitted premastered area that cannot be overwritten and a grooved user-writeable area that can be overwritten. The optical disc drive includes a first processor operable to communicate with a second processor, wherein the first processor includes instructions for performing non-time-critical tasks, and the second processor includes instructions for performing time-critical tasks, such as reading from and writing to optical media in the disc drive. The first processor monitors the status of the time critical tasks in the second processor and transmits commands to perform operations in the second processor. The first processor also controls power mode, manages recovery from errors, controls focus, tracking/seeking, spin, physical sector address (PSA), a laser, adjusts gains, and monitor cartridge load/eject. The first processor can be used to perform other tasks while it is waiting to receive a notice of a new command, a notify event, or a performance event.

Cross-Reference to CD-ROM Appendix

[0001] CD-ROM Appendix A, which is a part of the present disclosure, isa CD-ROM appendix consisting of 22 text files. CD-ROM Appendix Aincludes a software program executable on a controller as describedbelow. The total number of compact disks including duplicates is two.Appendix B, which is part of the present specification, contains a listof the files contained on the compact disk. The attached CD-ROM AppendixA is formatted for an IBM-PC operating a Windows operating system.

[0002] A portion of the disclosure of this patent document containsmaterial which is subject to copyright protection. The copyright ownerhas no objection to the facsimile reproduction by anyone of the patentdocument or the patent disclosure, as it appears in the Patent andTrademark Office patent files or records, but otherwise reserves allcopyright rights whatsoever.

[0003] These and other embodiments are further discussed below.

CROSS-REFERENCE to CO-FILED APPLICATIONS

[0004] The present disclosure was co-filed with the following sets ofdisclosures: the “Tracking and Focus Servo System” disclosures, the“Servo System Calibration” disclosures, the “Spin Motor Servo System”disclosures, and the “System Architecture” disclosures; each of whichwas filed on the same date and assigned to the same assignee as thepresent disclosure, and are incorporated by reference herein in theirentirety. The Tracking and Focus Servo System disclosures include U.S.Disclosure Serial Nos. {Attorney Docket Nos. M-11095 US, M-12077 US,M-12078 US, M-12079 US, M-12080 US, M-12081 US, M-12082 US, M-12083 US,M-12084 US, M-12085 US, M-12086 US, M-12087 US, M-12088 US, M-12089 US,M-12090 US, M-12091 US, M-12092 US, M-12093 US, M-12104 US, M-12105 US,M-12106 US, M-12107 US, M-12108 US, M-12111 US, M-12112 US, and M-12195US.} The Servo System Calibration disclosures include U.S. DisclosureSerial Nos. {Attorney Docket Nos. M-11097 US, M-12094 US, M-12095 US,M-12096 US, M-12097 US, M-12098 US, M-12099 US, M-12100 US, M-12101 US,M-12102 US, M-12103 US, M-12109 US, M-12110 US and M-12155 US.} The SpinMotor Servo System disclosures include U.S. Disclosure Serial Nos.{Attorney Docket Numbers M-12117 US, M-12118 US, M-12119 US, M-11096 US,M-12121 US, M-12122 US, and M-12147 US.} The System Architecturedisclosures include U.S. Disclosure Serial Nos. {Attorney Docket NumbersM-11098 US, M-12120 US, M-12023 US, M-12024 US, M-12025 US, M-12026 US,M-12027 US, M-12028 US, M-12029 US, M-12030 US, M-12031 US, M-12032 US,and M-12177 US.}

[0005] The present disclosure was also co-filed with the followingdisclosures U.S. Patent Disclosure Serial Nos. ______, and ______{Attorney Docket Numbers M-9115, and M-12076 US, respectively}, each ofwhich was filed on the same date and assigned to the same assignee asthe present disclosure, and are incorporated by reference herein intheir entirety.

BACKGROUND

[0006] There is an ever increasing need for data storage devices havinggreater storage capacity with smaller form factors for multimediasystems utilizing text, video, and audio information. Further, there isa large demand for highly portable, rugged, and robust systems for useas multimedia entertainment, storage systems for PDAs, cell phones,electronic books, and other systems. One of the more promisingtechnologies for rugged, removable, and portable data storage is WORM(write once read many) optical disk drives.

[0007] One of the important factors affecting design of an opticalsystem (such as that utilized in a WORM drive) is the optical componentsutilized in the system and the control of actuators utilized to controlthe optical system on the disk. The optical system typically includes alaser or other optical source, focusing lenses, reflectors, opticaldetectors, and other components. Although a wide variety of systems havebeen used or proposed, typical previous systems have used opticalcomponents that were sufficiently large and/or massive that functionssuch as focus and/or tracking were performed by moving components of theoptical system.

[0008] Many early optical disks and other optical storage systemsprovided relatively large format read/write devices including, forexample, devices for use in connection with 12 inch (or larger) diameterdisks. As optical storage technologies have developed, however, therehas been increasing attention toward providing feasible and practicalsystems which are relatively smaller in size. Generally, a practicalread/write device must accommodate numerous items within its formfactor, including the media, media cartridge (if any), media spin motor,power supply and/or conditioning, signal processing, focus, tracking orother servo electronics, and components associated or affecting thelaser or light beam optics. Accordingly, in order to facilitate arelatively small form-factor, an optical head occupying small volume isdesirable. In particular, it is desirable for a small optical head inthe direction perpendicular to the surface of the spinning media.

[0009] Additionally, a smaller, more compact, optical head providesnumerous specific problems for electronics designed to control theposition and focus of the optical head including: the need for extensivedrive calibration and periodic drive recalibration, time critical servostate machines to compensate for the flexible focus and trackingactuators, nonlinear and cross-coupled tracking and focus positionsensors, dynamic crosscoupling between the multiple servo loops, needfor low power consumption to conserve battery life, removable andinterchangeable media, robust handling of media defects, presence ofboth pre-mastered and user writeable areas on the same disk, need tooperate in wide range of conditions including various physicalorientations, wide range of ambient temperatures and humidity levels,and the presence of shock and vibration.

[0010] Therefore, there is a need for an optical head with a small formfactor and, in addition, a servo system for controlling the head so thatdata can be reliably read from and written to the optical media.

SUMMARY

[0011] A system, method, and apparatus in accordance with the presentinvention includes a code architecture that addresses the designchallenges for the small form factor optical head. Embodiments of asystem and device in accordance with the present invention utilizeseveral unique methods including sharing a general purpose processorbetween the servo system and other drive systems in the device, using adedicated high speed processor for time critical servo functions,communicating between the dedicated servo processor and the sharedgeneral purpose processor, distributing the servo processing between thegeneral purpose processor and the dedicated servo processor, anddistributing the servo processing within the general purpose processorbetween a main loop process and a background periodic interrupt process.

[0012] In one embodiment, a system for coordinating time-critical tasksin a control system for an optical disc drive is provided for opticalmedia with a pitted premastered area that cannot be overwritten and agrooved user-writeable area that can be overwritten. The system includesseveral sets instructions operable to control handling of a new command,a notify event, or a performance event. The sets of instructions includeone or more of the following: a set of power mode state machineinstructions operable to control the power mode of the optical discdrive; a set of recovery manager instructions operable to attemptrecovery from an error detected while performing a command; a set offocus control state machine instructions operable to control closingfocus in the optical disc drive; a set of tracking/seeking control statemachine instructions operable to control closing track in the opticaldisc drive; a set of spin control state machine instructions operable tocontrol the spin speed of optical media in the optical disc drive; a setof physical sector address (PSA) state machine instructions operable todetermine the position of an actuator arm in relation to grooved andpitted areas in the optical media; a set of laser control state machineinstructions operable to control the power mode of a laser in theoptical disc drive; a set of adjust gains state machine instructionsoperable to adjust control system gains in the optical disc drive; a setof performance monitor state machine instructions operable to monitorthe status of the time critical tasks in the second processor; and a setof monitor load/eject state machine instructions to determine whetherthe optical media has been loaded or ejected from the optical discdrive.

[0013] In one aspect of this embodiment, a first processor operable tocommunicate with a second processor, wherein the first processorincludes: instructions operable to wait to receive a notice of at leastone of: the new command being issued to the second processor, the notifyevent, or the performance event; and instructions operable to controlthe rate at which the first processor monitors the status of timecritical tasks in the second processor.

[0014] In another aspect of this embodiment, the instructions in thefirst processor increase the rate at which the first processor monitorsthe status of the time critical tasks in the second processor uponreceiving the new command, the notify event, or the performance event.

[0015] In another aspect of this embodiment, the instructions in thefirst processor decrease the rate at which the first processor monitorsthe status of the time critical tasks in the second processor.

[0016] In another aspect of this embodiment, the instructions in thefirst processor decrease the rate at which the first processor monitorsthe status of the time critical tasks in the second processor once thenew command, the notify event, or the performance event has beenhandled.

[0017] In another aspect of this embodiment, the power mode statemachine instructions are operable to receive a request for at least oneof the following power modes: DSP only mode, minimum power mode, idlepower mode, and full power mode.

[0018] In another aspect of this embodiment, the power mode statemachine instructions are further operable to disable issuing aninterrupt related to an error condition in the second processor whenentering a second processor only power mode or a minimum power mode.

[0019] In another aspect of this embodiment, the power mode statemachine instructions are further operable to enable issuing an interruptrelated to an error condition in the second processor when entering afull power mode.

[0020] In another aspect of this embodiment, the power mode statemachine instructions are further operable to monitor ejection or loadingof a cartridge in the optical disc drive in minimum power mode.

[0021] In another aspect of this embodiment, the instructions areoperable to open tracking, focus, or spin servo control loops beforeentering a lower power mode.

[0022] In another embodiment, a method for coordinating time-criticaltasks in a control system for an optical disc drive is provided foroptical media with a pitted premastered area that cannot be overwrittenand a grooved user-writeable area that can be overwritten. The methodincludes controlling handling of a new command, a notify event, or aperformance event by at least one of the following: controlling thepower mode of the optical disc drive; attempting recovery from an errordetected while performing a command; controlling closing focus in theoptical disc drive; controlling closing track in the optical disc drive;controlling the spin speed of optical media in the optical disc drive;determining the position of an actuator arm in relation to grooved andpitted areas in the optical media; controlling the power mode of a laserin the optical disc drive; adjusting control system gains in the opticaldisc drive; monitoring the status of the time critical tasks in thesecond processor; and determining whether the optical media has beenloaded or ejected from the optical disc drive.

[0023] One aspect of this embodiment further comprises waiting toreceive a notice of at least one of: the new command being issued to thesecond processor, the notify event, or the performance event, andcontrolling the rate at which the first processor monitors the status oftime critical tasks in the second processor.

[0024] In another aspect of this embodiment, controlling the rate atwhich the first processor monitors the status of time critical tasks inthe second processor includes increasing the rate upon receiving the newcommand, the notify event, or the performance event.

[0025] In another aspect of this embodiment, controlling the rate atwhich the first processor monitors the status of time critical tasks inthe second processor includes decreasing the rate at which the firstprocessor monitors the status of the time critical tasks in the secondprocessor.

[0026] In another aspect of this embodiment, controlling the rate atwhich the first processor monitors the status of time critical tasks inthe second processor includes decreasing the rate once the new command,the notify event, or the performance event has been handled.

[0027] In another aspect of this embodiment, controlling the power modeof the laser in the optical disc drive includes receiving a request forat least one of the following power modes: DSP only mode, minimum powermode, idle power mode, and full power mode.

[0028] In another aspect of this embodiment, controlling the power modeof a laser in the optical disc drive includes disabling issuing aninterrupt related to an error condition in the second processor whenentering a second processor only power mode or a minimum power mode.

[0029] In another aspect of this embodiment, controlling the power modeof the laser includes enabling issuing an interrupt related to an errorcondition in the second processor when entering a full power mode.

[0030] In another aspect of this embodiment, controlling the power modeof a laser in the optical disc drive includes monitoring ejection orloading of a cartridge in the optical disc drive in minimum power mode.

[0031] Another aspect of this embodiment includes opening tracking,focus, or spin servo control loops before entering a lower power mode.

[0032] The methods in accordance with the present invention can beembodied in the form of computer-implemented processes and apparatusesfor practicing those processes. The methods can also be embodied in theform of computer program code embodied in tangible media, such as floppydiskettes, CD-ROMS, hard drives, or any other computer-readable storagemedium where, when the computer program code is loaded into and executedby a computer, the computer becomes an apparatus for practicing theinvention. The method can also be embodied in the form of computerprogram code, for example, whether stored in a storage medium, loadedinto and/or executed by a computer, or transmitted over sometransmission medium, such as over electrical wiring or cabling, throughfiber optics, or via electromagnetic radiation, wherein, when thecomputer program code is loaded into and executed by a computer, thecomputer becomes an apparatus for practicing the invention. Whenimplemented on a general-purpose microprocessor, the computer programcode segments configure the microprocessor to create specific logiccircuits.

[0033] The above as well as additional objectives, features, andadvantages of embodiments of the present invention will become apparentin the following detailed written description.

SHORT DESCRIPTION OF THE FIGURES

[0034]FIG. 1a shows an optical drive with which various embodiments of adisc drive control system in accordance with the present invention maybe utilized.

[0035]FIG. 1b shows a diagram for an optical media that may be utilizedin the disc drive shown in FIG. 1.

[0036]FIG. 2a shows an embodiment of an optical pickup unit mounted onan actuator arm that can be utilized with the optical drive shown inFIG. 1.

[0037]FIGS. 2b shows an embodiment of the optical pick-up unit that canbe utilized with the optical drive shown in FIG. 1.

[0038]FIG. 2c illustrates the optical path through the optical head ofFIG. 2b.

[0039]FIG. 2d shows an embodiment of optical detector positioning of theoptical pick-up of FIG. 2b.

[0040]FIG. 3 is a block diagram of components for processing signals ina disc drive control system in accordance with the present invention.

[0041]FIGS. 3a through 3 g show examples of mailbox messages that can becommunicated between components shown in FIG. 3 in accordance with thepresent invention.

[0042]FIG. 4 is a block diagram of components included in the signalprocessing system shown in FIG. 3.

[0043]FIGS. 4a through 4 p show examples of servo commands that can beimplemented in the signal processing system shown in FIGS. 3 and 4.

[0044]FIG. 5 shows a block diagram of an embodiment of the servo threadshown in FIG. 4.

[0045]FIG. 6 shows a block diagram of an embodiment of the commandhandler shown in FIG. 5.

[0046]FIG. 7 shows a block diagram of an embodiment of the event handlershown in FIG. 5.

[0047]FIG. 8 shows a block diagram of an embodiment of the performanceevent handler shown in FIG. 5.

[0048]FIG. 8a shows a block diagram of an embodiment of the servorecalibration process as shown in FIG. 8.

[0049]FIG. 9 shows a block diagram of an embodiment of the heartbeatinterrupt shown in FIG. 4.

[0050]FIG. 10 shows a block diagram of an embodiment of the power modecontrol state machine shown in FIG. 9. FIG. 11 shows a block diagram ofan embodiment of the recovery manager shown in FIG. 9.

[0051]FIG. 11a shows a diagram of an embodiment of a recovery statemachine for the recovery manager shown in FIG. 11.

[0052]FIG. 12a shows a diagram of an embodiment of an off formatdetection manager that is executed as part of the classify problem state1106′ in FIG. 1a.

[0053]FIG. 12b shows a diagram of components utilized to perform offformat detection for the off format detection manager shown in FIG. 12a.

[0054]FIG. 12c shows a diagram of an embodiment of logic to perform offformat detection for the off format detection manager shown in FIG. 12a.

[0055]FIGS. 13a, 13 b, and 13 c show diagrams of aspects of thetracking/seeking control state machine shown in FIG. 9.

[0056]FIGS. 14a, 14 b, and 14 c show diagrams of aspects of the focuscontrol state machine shown in FIG. 9.

[0057]FIG. 15 shows a diagram of an embodiment of the spin control statemachine shown in FIG. 9.

[0058]FIG. 16 shows a diagram of an embodiment of the physical sectoraddress state machine shown in FIG. 9.

[0059]FIG. 17 shows a diagram of an embodiment of the laser controlstate machine shown in FIG. 9.

[0060]FIG. 18 shows a diagram of an embodiment of the adjust gains statemachine shown in FIG. 9.

[0061]FIG. 19 shows a diagram of an embodiment of the continuousperformance monitor state machine shown in FIG. 9.

[0062]FIG. 20a shows a diagram of logic included in an embodiment of theDSP status mailbox interrupt handler shown in FIG. 4.

[0063]FIG. 20b shows a diagram of logic included in an embodiment of amailbox interrupt service routine that can be included in the DSP statusmailbox interrupt handler shown in FIG. 20a.

[0064]FIG. 20c shows a diagram of additional logic included in anembodiment of a mailbox interrupt service routine that can be includedin the DSP status mailbox interrupt handler shown in FIG. 20a.

DETAILED DESCRIPTION

[0065] Optical Disk Drive Overview

[0066]FIG. 1a shows an optical drive 100 in accordance with the presentinvention. Optical drive 100 includes a spin motor 101 (called spindledriver on FIG. 1) on which an optical media 102 is mounted. Drive 100further includes an optical pick-up unit (OPU) 103 mechanicallycontrolled by an actuator arm 104. OPU 103 includes a light sourceelectrically controlled by laser driver 105. OPU 103 further includesoptical detectors providing signals for controller 106. Controller 106can control the rotational speed of optical media 102 by controllingspin motor 101, the position and orientation of OPU 103 through actuatorarm 104, and the optical power of the light source in OPU 103 bycontrolling laser driver 105.

[0067] Controller 106 includes R/W processing 110, servo system 120, andinterface 130. R/W processing 110 controls the reading of data fromoptical media 102 and the writing of data to optical media 102. R/Wprocessing 110 outputs data to a host (not shown) through interface 130.Servo system 120 controls the speed of spin motor 101, the position ofOPU 103, and the laser power in response to signals from R/W processing110. Further, servo system 120 insures that the operating parameters(e.g., focus, tracking, and spin motor speed) are controlled in orderthat data can be read from or written to optical media 102.

[0068] Optical media 102 can include pre-mastered portions and writeableportions. Premastered portions, for example, can be written at the timeof manufacture to include content provided by a content provider. Thecontent, for example, can include audio data, video data, text data, orany other data that can be provided with optical media 102. Thewriteable portion of optical media 102 can be written onto by drive 100to provide data for future utilization of optical media 102. The user,for example, may write notes or other information on the disk. Drive100, for example, may write calibration data or other operating data tothe disk for future operation of drive 100 with optical media 102. Anexample of optical media 102 is described in U.S. application Ser. No.09/560,781 for “Miniature Optical Recording Disk”, herein incorporatedby reference in its entirety, The R/W Data Processing 110 can operatewith many different disk formats. One example of a disk format isprovided in U.S. application Ser. No. 09/527,982, for “CombinationMastered and Writeable Medium and Use in Electronic Book InternetAppliance,” herein incorporated by reference in its entirety. Otherexamples of disk data formats are provided in U.S. application Ser. No.[Attorney Docket No. M-8374 US], “File System Management Method;” U.S.application Ser. No. 09/583,448, “Disk Format for Writeable MasteredMedia;” U.S. application Ser. No. [Attorney Docket No. M-8379 US],“Structure and Method for Storing Data on Optical Disks;” U.S.application Ser. No. 09/542,510 for “Embedded Data Encryption Means;”U.S. application Ser. No. 09/583,133 for “Read Write File SystemEmulation;” and U.S. application Ser. No. [Attorney Docket No. M-8376US] for “Storage Device With Embedded Encryption Means,” each of whichis hereby incorporated by reference in its entirety.

[0069] Drive 100 can be included in any host, for example personalelectronic devices. Examples of hosts that may include drive 100 arefurther described in U.S. patent application Ser. No. 09/315,398 forRemovable Optical Storage Device and System, herein incorporated byreference in its entirety. In some embodiments, drive 100 can have arelatively small form factor such as about 10.5 mm height, 50 mm widthand 40 mm depth.

[0070]FIG. 1b shows an example of optical media 102. Optical media 106can include any combinations of pre-mastered portions 150 and writeableportions 151. Premastered portions 150, for example, can be written atthe time of manufacture to include content provided by a contentprovider. The content, for example, can include audio data, video data,text data, or any other data that can be provided with optical media102. Writeable portion 151 of optical media 102 can be written onto bydrive 100 to provide data for future utilization of optical media 102.The user, for example, may write notes, keep interactive status (e.g.for games or interactive books) or other information on the disk. Drive100, for example, may write calibration data or other operating data tothe disk for future operations of drive 100 with optical media 102. Insome embodiments, optical media 102 includes an inner region 153 closeto spindle access 152. A bar code can be written on a portion of aninner region 153. The readable portion of optical media 102 starts atthe boundary of region 151 in FIG. 1b. In some embodiments, writeableportion 151 may be at the outer diameter rather than the inner diameter.In some embodiments of optical media 102, an unusable outer region 154can also be included.

[0071] The pre-mastered portions 150 of the optical media 102 can have adifferent data density compared to the writeable portions 151. Dataprocessors in disc drive 100 can therefore use different clock ratesdepending on whether the pre-mastered portions 150 or the writeableportions 151 are being accessed. Disc drive 100 must also be able toread and write data at variable density. Further, each time a newcartridge containing the optical media 102 is inserted, drive 100 mustdetermine if different densities are included on the optical media 102,and adjust drive parameters if the data densities are different from theoptical media 102 previously used.

[0072]FIG. 2a shows an embodiment of actuator arm 104 with OPU 103mounted on one end. Actuator arm 104 in FIG. 2a includes a pin 200 whichprovides a rotational pivot about axis 203 for actuator arm 104.Actuator 201, which in some embodiments can be a magnetic coilpositioned over a permanent magnet, can be provided with a current toprovide a rotational motion about axis 203. Actuator arm 104 furtherincludes a flex axis 204. A motion of OPU 103 substantiallyperpendicular to the rotational motion about axis 203 can be provided byactivating actuator coil 206. In some embodiments, actuators 206 and 201can be voice coils.

[0073]FIGS. 2b and 2 c show an embodiment of OPU 103. OPU 103 of FIG. 2bincludes a periscope 210 having reflecting surfaces 211, 212, and 213.Periscope 210 is mounted on a transparent optical block 214. Object lens223 is positioned on spacers 221 and mounted onto quarter wave plate(QWP) 222 which is mounted on periscope 210. Periscope 210 is, in turn,mounted onto turning mirror 216 and spacer 224, which are mounted on asilicon submount 215. A laser 218 is mounted on a laser mount 217 andpositioned on silicon submount 215. Further, detectors 225 and 226 arepositioned and mounted on silicon substrate 215. In some embodiments, ahigh frequency oscillator (HFO) 219 can be mounted next to laser 218 onsilicon submount 215 to provide modulation for the laser beam output oflaser 218.

[0074] Laser 218 produces an optical beam 224 which is reflected intotransparent block 210 by turning mirror 216. Beam 224 is then reflectedby reflection surfaces 212 and 213 into lens 223 and onto optical medium102 (see FIG. 1). In some embodiments, reflection surfaces 212 and 213can be polarization dependent and can be tuned to reflect substantiallyall of the light from laser 218. QWP 222 rotates the polarization oflaser beam 224.

[0075] The reflected beam 230 from optical medium 102 is collected bylens 223 and focused into periscope 210. A portion (in some embodimentsabout 50%) of reflected beam 230 passes through reflecting surface 213and is directed onto optical detector 226. Further, a portion ofreflected beam 230 passes through reflecting surface 212 and isreflected onto detector 225 by reflecting surface 211. Because of thedifference in path distance between the positions of detectors 225 and226, detector 226 is positioned before the focal point of lens 223 anddetector 225 is positioned after the focal point of lens 223, as isshown in the optical ray diagram of FIG. 2c.

[0076]FIG. 2d shows an embodiment of detectors 225 and 226 in accordancewith the present invention. Detector 225 includes an array of opticaldetectors 231, 232, and 233 positioned on a mount 215. Each individualdetector, detectors 231, 232, and 233, is electrically coupled toprovide signals A, E and C to controller 106. Detector 226 also includesan array of detectors, detectors 234, 235 and 236, which provide signalsB, F, and D, respectively, to controller 106. In some embodiments,center detectors 232 and 235, providing signals E and F, respectively,are arranged to approximately optically align with the tracks of opticalmedia 102 as actuator arm 104 is rotated across optical media 102.

[0077] The degree of focus, then, can be determined by measuring thedifference between the sum of signals A and C and the center signal E ofdetector 225 and the difference between the sum of signals B and D andthe center signal F of detector 226. A tracking monitor can be providedby monitoring the difference between signals A and C of detector 225 andthe difference between signals B and D of detector 226. Embodiments ofOPU 103 are further described in U.S. application Ser. No. 09/540,657for “Low Profile Optical Head,” herein incorporated by reference in itsentirety.

[0078] Embodiments of drive 100 (FIG. 1) present a multitude of controlsystem challenges over conventional optical disk drive systems. Aconventional optical disk drive system, for example, performs atwo-stage tracking operation by moving the optics and focusing lensradially across the disk on a track and performs a two-stage focusingoperation by moving a focusing lens relative to the disk. Actuators 201and 206 of actuator arm 104 provide a single stage of operation which,nonetheless in some embodiments, performs with the same performance asconventional drives with conventional optical media. Further,conventional optical disk drive systems are much larger than someembodiments of drive 100. Some major differences include the actuatorpositioning of actuator arm 104, which operates in a rotary fashionaround spindle 200 for tracking and with a flexure action around axis204 for focus. Further, the speed of rotation of spindle driver 101 isdependent on the track position of actuator arm 104. Additionally, thecharacteristics of signals AR, BR, CR, DR, ER, and FR received from OPU103 differ with respect to whether OPU 103 is positioned over apre-mastered portion of optical media 102 or a writeable portion ofoptical media 102. Finally, signals AR, BR, CR, DR, ER, and FR maydiffer between a read operation and a write operation.

[0079] It may generally be expected that moving to a light-weightstructural design from the heavier and bulkier conventional designs,such as is illustrated with actuator arm 104, for example, may reducemany problems involving structural resonances. Typically, mechanicalresonances scale with size so that the resonant frequency increases whenthe size is decreased. Further, focus actuation and tracking actuationin actuator arm 104 are more strongly cross-coupled in actuator arm 104,whereas in conventional designs the actuator and tracking actuation ismore orthogonal and therefore more decoupled. Further, since all of theoptics in drive 100 are concentrated at OPU 103, a larger amount ofoptical cross-coupling between tracking and focus measurements can beexperienced. Therefore, servo system 120 has to push the bandwidth ofthe servo system as hard as possible so that no mechanical resonances inactuator arm 104 are excited while not responding erroneously tomechanical and optical cross couplings. Furthermore, due to the loweredbandwidth available in drive 100, non-linearities in system response canbe more severe. Further, since drive 100 and optical media 102 aresmaller and less structurally exact, variations in operation betweendrives and between various different optical media can complicatecontrol operations on drive 100.

[0080] One of the major challenges faced by servo system 120 of controlsystem 106, then, include operating at lower bandwidth with largeamounts of cross coupling and nonlinear system responses from operatingcloser to the bandwidth, and significant variation between optical mediaand between different optical drives. Additionally, the performance ofdrive 100 should match or exceed that of conventional CD or DVD drivesin terms of track densities and data densities. Additionally, drive 100needs to maintain compatibility with other similar drives so thatoptical media 102 can be removed from drive 100 and read or written toby another similar drive.

[0081] Most conventional servo systems are analog servos. In an analogenvironment, the servo system is limited with the constraints of analogcalculations. Control system 106, however, can include substantially adigital servo system. A digital servo system, such as servo system 120,has a higher capability in executing solutions to problems of systemcontrol. A full digital servo system is limited only by the designer'sability to write code and in the memory storage available in which tostore data and code. Embodiments of servo system 120, then, can operatein the harsher control environment presented by disk drive 100 and arecapable of higher versatility towards upgrading servo system 120 and forrefinement of servo system 120 compared to conventional systems.

[0082] Further requirements for drive 100 include error recoveryprocedures. Embodiments of drive 100 which have a small form factor canbe utilized in portable packages and are therefore subject to severemechanical shocks and temperature changes, all of which affect theability to extract data (e.g., music data) from optical media 102reliably or, in some cases, write reliably to optical media 102. Overallerror recovery and control system 106 is discussed below, whiletracking, focus, seek, and calibration processes are discussed in theapplication entitled “Tracking, Focus, and Seek Functions withCalibration Processes in a Servo System for an Optical Disk Drive”.

[0083] Control System Signal Processing Overview

[0084] Referring now to FIG. 3, a block diagram of components includedin a system for processing signals in a disc drive control system isshown including processor 302, digital signal processor (DSP) 304, andmailbox 306. Processor 302 performs diagnostic and other non-timecritical functions, while DSP 304 performs functions that are timecritical. Processor 302 and DSP 304 can be co-located on the same chipand, in one embodiment, can communicate via mailbox 306. In otherembodiments, processor 302 and DSP 304 can communicate via othersuitable means such as a data bus, serial interface, or shared,dual-ported memory. ST Microelectronics model number 34-00003-03 is anexample of a microprocessor chip that is suitable for use as processor302 and DSP 304.

[0085] DSP 304 can be slaved to processor 302, which performs overallcontrol functions along with calibration and error recovery functions.DSP 304 includes instructions for controlling the focus and tracking ata very high sample speed, and it also generates high order compensationsignals. Processor 302 takes over control when errors are detected andcomponents in the servo system 120 (FIG. 1a) need to be adjusted oroperation is to be discontinued. Processor 302 issues commands to DSP304 via mailbox 306, and DSP 304 uses mailbox 306 to provide informationto processor 302 regarding how well it is performing the requestedfunctions.

[0086] In one embodiment, processor 302 receives defect signal 308, spinvelocity signal 310, and angular spin speed signal 312, and outputs spincontrol signal 314, spin and tracking bias signal 316, and laser controlsignal 318. Processor 302 also outputs reset signal 320 to reinitializeDSP 304. DSP 304 receives angular spin speed signal 312, laser powersignal 322, optical signals 324, mirror signal 326, track crossingsignal 328, and defect signal 308. Output signals from DSP 304 includefocus control signal 328, diagnostic signal 330, track control signal332, and write abort signal 334.

[0087] In one embodiment, mailbox 306 utilizes interrupts to interfacewith DSP 304 and processor 302. In one implementation, a fixed number ofmailbox interrupts are available, and each mail box interrupt can beassigned to communicate a certain message. In other implementations, themessage communicated by a mailbox interrupt can vary, and a variablenumber of mailbox interrupts can be available. (In anotherimplementation, an interrupt can be generated by the DSP 304 whenever itwrites to one of its mailbox registers.) FIGS. 3a through 3 g showexamples of mailbox messages that can be communicated between processor302 and DSP 304 via mailbox 306.

[0088]FIG. 3a shows examples of messages in processor write/DSP readmailbox 340 with sixteen slots for outgoing messages from processor 302to DSP 304. In one embodiment, these registers can be read or written bythe processor 302, but they can only be read by the DSP 304. The firstthree mailbox messages are DSP control registers, as defined in FIGS. 3bthrough 3 d. Each of the three control registers include sixteen bitsthat can be set or cleared to control focus, track, and seek functions,to provide signal and trace addresses, compensation parameters, andon/off switches for read/write components such as the laser. Examples ofother messages in mailbox 340 include acceleration parameters, offsetand shift values for focus and track gain parameters, sensor thresholddetection values, and crosstalk compensation.

[0089]FIG. 3e shows examples of messages in processor read/DSP writemailbox 342 with sixteen slots for messages from DSP 304 to processor302. The messages are used to convey information regarding focus, track,and seek errors. In one embodiment, these registers can be read orwritten by the DSP 304 but they can only be read by the processor 302.Write mailbox 342 includes one or more status registers with bits thatcan be set to convey the status of focus, track, and seek operations asshown, for example, in FIGS. 3f and 3 g.

[0090] Note that other messages and registers can be included inaddition to, or instead of, the messages and registers shown in FIGS. 3athrough 3 g.

[0091] Referring now to FIG. 4, a diagram of one embodiment of codecomponents included in processor 302 is shown. The code componentsrepresent sets of instructions that can be implemented in software,firmware, hardware, or a combination of software, firmware and hardware,as known in the art. In one embodiment, the components can include servothread 404, real-time operating system (RTOS) 406, heartbeat interrupt408, DSP status mailbox interrupt handler 410, spin control interrupts412, and utility threads 414 that include read/write thread 416,asynchronous input/output (async I/O) thread 418, diagnostic thread 420,timer thread 422, interface thread 424, and file system manager 426.

[0092] Heartbeat interrupt 408 executes periodically at a variable rate,for example, a rate of 20 Hz during sleep mode to a rate of 0.5 KHzduring exercise mode. The rates to be used for different modes can bedetermined based on the processing load, the frequencies associated withthe servo, and the processing capacity of processor 302. The heartbeatinterrupt 408 includes: a focus state machine to control the performanceof the focus servo such as closing and opening focus; a tracking statemachine to control the performance of the tracking servo such as turningtracking on/off and seeking; a spin state machine to control theperformance of the spin servo such as turning spin on and off; aphysical sector addresses (PSA) state machine to manage the reading ofphysical sector addresses; a performance monitoring state machine torequest a performance event or adjust drive parameters if poorperformance is detected; a power management state machine to transitionbetween the various power states of the drive; a monitor laser statemachine to coordinate the laser power with drive mode of operation; anadjust gains state machine to load the best focus and tracking gainsbased on the position of the actuator arm 104; and a load/eject statemachine to manage the loading and unloading of a cartridge containingoptical media 102.

[0093] DSP 304 issues messages that can include data and/or DSP statusinformation to mailbox 306. DSP status mailbox interrupt handler 410receives DSP status information and can request a notify event or atracking event to RTOS 406, as required. The data and status informationfrom mailbox 306 can be accessed by servo thread 404 and heartbeatinterrupt 408.

[0094] The command handler in servo thread 404 initiates actions forperforming different types of commands, including data transfer commandsassociated with reading from and writing to media 102 (FIG. 1a), anddiagnostic commands for verifying the functionality of drive 100 (FIG.1a) during engineering development, as well as during operation by auser. FIGS. 4a through 4 p show examples of data transfer and diagnosticcommands that can be implemented in servo system 120 (FIG. 1a).Diagnostic commands can be included to control spin speed, test andcalibrate various components, open and close track and focus, turnvarious components on and off, set gain, offset, and compensationparameters, and error recovery. Data transfer commands can be includedto seek, spin up, spin down, load/eject a media cartridge, and calibrateservo system 120. The data transfer and diagnostic commands can includeone or more parameters, as shown in FIGS. 4a through 4 p. Note thatother commands can be included in addition, or instead of, the commandsshown in FIGS. 4a through 4 p.

[0095] The event handler in servo thread 404 facilitates communicationbetween code components in processor 302. In one embodiment, real-timeoperating system (RTOS) 406 issues servo events to the event handler.One servo event is the notify event which can be issued to RTOS 406 by aservo periodic heart beat interrupt 408 or the DSP status mailboxinterrupt handler 410. A notify event issued by the DSP status mailboxinterrupt handler 410 indicates that although no command is currentlyactive, an error has been detected that requires attention. A notifyevent can be issued by the heartbeat interrupt 408 to indicate whether acommand could be completed.

[0096] As an example of how notify event requests issued by DSP statusmailbox interrupt handler 410 can be handled, assume drive 100 (FIG. 1a)is tracking and focus is closed when a shock, such as knocking drive100, causes loss of focus. The DSP 304 includes code to compensate fortracking and focus errors, and to determine whether focus or trackinghave been lost. When the DSP 304 detects lost focus, one or more DSPstatus registers, such as Bit 5 in the DSP status register shown in FIG.3f, in mailbox 306 are set accordingly. The mailbox 306 sends the DSPstatus message to DSP status mailbox interrupt handler 410, which issuesa request for a notify event to RTOS 406. The RTOS 406 issues a notifyevent to alert the servo thread 404. The event handler in servo thread404 then issues one or more commands to heartbeat interrupt 408 andmailbox 306 to take appropriate action, such as attempting to re-closefocus.

[0097] RTOS 406 can issue a command waiting event to indicate that acommand has been issued to servo thread 404 to perform a drive function,such as spinning up the drive 100 (FIG. 1a). Another event is a switchesevent to indicate that the cartridge containing optical media 102 (FIG.1a) is being inserted or ejected from drive 100. RTOS 406 can also issuespin, focus, and tracking events to servo thread 404 in response torequests for spin, focus, and tracking events issued by their respectivestate machines in heartbeat interrupt component 408. Such event requestsare typically issued in response to completing, or failing to complete,a command.

[0098] As an example of how a spin, focus or tracking event can behandled, assume one of the utility threads 414 issues a servo commandmessage to the RTOS 406, and the RTOS 406 issues a command waiting eventto the servo thread 404. The command handler in servo thread 404subsequently issues a control command to the heartbeat interrupt 408.When the heartbeat interrupt 408 completes the command, it requests anevent corresponding to the command, such as a spin, focus, or trackingevent, from RTOS 406. The RTOS 406 generates the requested event andsends it to the servo thread 404. A servo command status is then sentfrom servo thread 404 to the corresponding utility thread 414.

[0099] Heartbeat interrupt 408 also includes a recovery state machine.In one implementation, the recovery state machine advantageously enablescommands to be resumed where they left off after a problem has beendetected and corrected. For example, if a problem with closing focus isdetected while a read command is being processed, the recovery statemachine saves the current state of the drive 100 (FIG. 1a), corrects thefocus problem, clears error indications, and restores the state of drive100 to resume the read command where it left off.

[0100] In one embodiment, the functions performed by utility threads 414include the following: Spin Control Interrupts 412 measure the currentspindle speed, determine the correct spindle speed based on currenttrack position, and calculate the control signals to maintain a constantspeed or to change spindle speeds; Read/Write Thread 416 manages thereading of data from the disk and the writing of data to the disk; AsyncI/O Thread 418 is utilized primarily in engineering testing to managethe transfer of data from a user data input device, such as a keyboard,over an interface to the drive 100; Diagnostic Thread 420 executesdiagnostic commands, which are used primarily during engineeringtesting; Timer Thread 422 provides timing utilities used by the otherthreads; Interface Thread 424 manages the communication and datatransfer between the drive and the host; and File System 426 manages theorganization of data on the optical disc 102 (FIG. 1a).

[0101] Servo Thread

[0102] Referring now to FIGS. 3, 4, and 5, an embodiment of main loop500 in servo thread 404 is shown including an initialization path 502and a continuous path 504. Initialization path 502 includes process 506to initialize servo random access memory (RAM) variables, and process508 to initialize the frame rate of the heartbeat interrupt 408 based ona clock (not shown) in processor 302.

[0103] Processor 302 can include different power modes such as sleepmode (low power consumption), high power mode, and operating mode. Inone implementation, processor 302 loads program code into DSP 304 everytime power is turned on in process 510 and then enters high power modein process 512. In other embodiments, program code in DSP 304 can bepreloaded, and/or implemented in firmware or in hardware circuitry,eliminating the need for process 510.

[0104] Initialization path 502 can also include process 514 toinitialize processing components associated with a spin motor driver forspin motor 101 in servo system 120 (FIG. 1a) as further described in TheSpin Motor Servo System disclosures.

[0105] Initialization path 502 can also include processes 516, 518, and520 to retrieve and load calibration values. Two or more different setsof calibration values may be available, including values that were setduring manufacture, values that were in use before the last power down,as well as updated values that are generated during power up.Alternatives for determining which set, or combination of sets, ofcalibration values to use are described in The Servo System Calibrationdisclosures.

[0106] Initialization path 502 can also include processes 524 and 526 toinitialize the actuator arm 104 (FIG. 1 a) to the center of the opticalmedia 102 (FIG. 1a) and move the OPU 103 (FIG. 1a) to a position awayfrom media 102. Process 528 places servo system 120 (FIG. 1a) in aminimum power mode to conserve power while drive 100 is in idle mode.Process 530 enables heartbeat interrupt 408 and transfers control tocontinuous path 504.

[0107] In one embodiment, process 532 in continuous path 504 stays idleuntil a new event is received, such as a command event, a notify eventdue to an error that has been detected, or a performance event due to aproblem with performing a command. In one implementation, process 532can release processor 302 for use by other processing tasks until anevent is received.

[0108] When process 532 does receive an event, process 534 can increasethe heartbeat rate. For example, if process 532 was waiting with a slow“resting” heartbeat rate of 20 Hz, the “exercise” heartbeat rate can beincreased to 0.5 KHz. Depending on whether a command event, a notifyevent, or a performance event was received, the RTOS 406 can issue theevent to servo thread 404 (FIG. 4), which subsequently invokes thecorresponding handler, i.e., command handler 536, event handler 538, orperformance event handler 540.

[0109] Once the actions associated with the event have been executed,process 544 reduces the heartbeat rate and suspends execution of mainloop 504 by returning control to process 532 until another event isreceived. Servo thread 404 can release processor 302 when it is waitingfor a command or event, thereby preserving bandwidth of processor 302for use by other components in drive 100 (FIG. 1a).

[0110] Command Handler

[0111]FIG. 6 shows an example of processes that can be included in oneembodiment of command handler 536. Referring to FIGS. 4 and 6, duringeach pass of command handler 536, a command status and servo systemstatus message is sent to utility threads 414. The utility threads 414determine the actions to be performed, and transmit servo commandmessages to RTOS 406 as required, as indicated by process 602. RTOS 406issues a command waiting event to servo thread 404, which waits for theevent in process 604. When the command waiting event is received,process 606 sets a servo command active and a servo error state flag toindicate that a command is being processed.

[0112] The first pass through command handler 536, process 608 beginsexecuting the command in servo thread 404 by issuing a state machinecontrol message to the state machines in heartbeat interrupt 408.Heartbeat interrupt 408 issues an event request to RTOS 406, and servothread 404 waits for the event from RTOS 406. Command handler 536 thendetermines which event was received in process 610. If the event was aspin, focus, or tracking event, process 612 checks the command status.If the command was completed with no errors, processes 614 and 616 clearthe servo error state flag and the servo command active flag,respectively, and a command done event is requested from RTOS 406. RTOS406 issues the command done event to the utility thread 414 that issuedthe command message.

[0113] Referring again to process 610, if a notify or a time-out eventis received while a command is being processed, process 620 initiatesrecovery for the notify event by transferring control to the recoverystate machine in heartbeat interrupt 408. The functions performed by therecovery state machine are described hereinbelow. The recovery statemachine issues event requests to communicate whether the recoveryattempt is complete, or whether it failed to RTOS 406.

[0114] RTOS 406 issues a recovery event indicating whether recoverycompleted or failed to servo thread 404. Servo thread 404 waits foreither a recovery complete or recovery failed event and then transferscontrol to process 622. If recovery completed, process 622 transmits therecovery complete message to process 612. If the command was notcompleted after recovery, process 612 transfers control to process 624,which continues executing the command that was being processed when thenotify event was received. Referring back to process 622, if therecovery process failed, process 628 sets the servo error state toindicate that the command failed, and process 616 clears the servocommand active flag before control is transferred out of command handler536.

[0115] Referring again to process 610, if a command abort event isreceived, process 626 replaces the command currently being processedwith an abort command, and transfers control to process 624. The abortcommand executes in the servo thread 404. One of the first actionsperformed is to turn the tracking servo off. Servo thread 404 changesthe state of the tracking state machine executing in the heartbeatinterrupt 408 and then waits for a tracking event. The tracking statemachine completes a sequence of operations to open the tracking servoloop, as further discussed hereinbelow. When the tracking servo loopopens, the tracking state machine requests the RTOS 406 to issue atracking event. The RTOS generates the tracking event, which is receivedby the abort command executing in the servo thread 404. After thetracking loop opens, the servo thread 404, heartbeat interrupt 408 andRTOS 406 coordinate efforts, in a fashion similar to that used to openthe tracking loop, to open the focus loop. Once the focus loop opens,the laser 218 (FIG. 2) is shut off. Next, the servo thread 404,heartbeat interrupt 408, and RTOS 406 again coordinate efforts to openthe spin loop.

[0116] Event Handler

[0117]FIG. 7 shows an embodiment of event handler 538 that is executedby servo thread 404 when a notify event is received in process 702. Inone embodiment, requests for notify events are issued by heartbeatinterrupt 408 and mailbox interrupt 306 when a problem or error isdetected. RTOS 406 then issues the notify event to servo thread 404. Inone embodiment, process 704 monitors the time between the notify eventsand the number of notify events in order to avoid excessive recovery.The parameters for determining when a recovery attempts become excessivecan be set based on a number of different criteria, such as number ofrecovery attempts within a predetermined time period. For example, fiverecovery attempts within five seconds can be considered excessive in oneembodiment, while other parameters and values can be used in otherembodiments.

[0118] If the recovery is not excessive, process 706 initiates recoveryfor the notify event by transferring control to the recovery statemachine in heartbeat interrupt 408. The functions performed by therecovery state machine are described hereinbelow. The recovery statemachine issues event requests to communicate whether the recoveryattempt is complete, or whether it failed, to RTOS 406.

[0119] RTOS 406 issues a notify event indicating whether recoverycompleted or failed to servo thread 404. Process 708 directs controlbased on which event is received. If recovery completed, the eventhandler is finished, and process 708 returns control to servo thread404. If the recovery attempt failed, process 708 transfers control toservo thread 404, which processes an abort command. Note that the abortcommand in servo thread 404 can also be executed if additional recoverywould be excessive. In one embodiment, servo thread 404 issues a statemachine control message to heartbeat interrupt 408. Heartbeat interrupt408 requests the first of a series events, such as a notify event, toRTOS 406. RTOS 406 issues the requested event to servo thread 404, andprocess 710 determines whether the abort command processing is complete.

[0120] In one embodiment, processing an abort command includes heartbeatinterrupt 408 issuing a series of event requests including the notifyevent request described above, a spin event request, a focus eventrequest, and a tracking event request. The event requests are issued bythe state machines in heartbeat interrupt 408 when they finish tasksassociated with the abort command, such as turning off track, focus, andspin. The event requests can also be issued by DSP status mailboxinterrupt handler 410 when the DSP 304 detects a problem with theoperation of drive 100. Other event requests, such as turning off powerto the laser 218 (FIG. 2b), can also be implemented. These eventrequests can be issued sequentially, or one or more events can be issuedsimultaneously, depending on the capability of RTOS 406 to process eventrequests in parallel or as a batch. For each event request, RTOS 406issues a corresponding event to servo thread 404. As each event, orgroup of events is received, process 710 determines whether the abortcommand processing is complete, or whether the time allowed to processthe abort command has been exceeded. When the abort command processingis complete, or the abort command times out before it is complete, theevent handler 538 is finished, and control returns to servo thread 404.

[0121] Performance Event Handler

[0122]FIG. 8 shows an embodiment of performance event handler 540 whichis invoked when a performance event is sent to servo thread 404 (FIG.4). A performance event occurs when one of the state machines inheartbeat interrupt 408 (FIG. 4) detect a problem or error that may becorrected by recalibrating drive 100 (FIG. 1a). For example, if drive100 (FIG. 1a) was initially powered on and calibrated indoors in anenvironment with a warm ambient temperature, and then used outside in acold ambient temperature, the calibration values being used may not beoptimal for the colder environment. Several different levels ofrecalibration processes can be performed depending on the severity ofthe error, ranging from relatively low level of effort, to more complexprocesses requiring greater effort.

[0123]FIG. 8a shows one implementation of servo recalibration process802 that includes 6 different recalibration levels. Increased effort isundertaken to correct the detected error at each increasingrecalibration level. The recalibration processes are further describedin The Servo System Calibration disclosures. Switch 804 branches to thecurrent recalibration level. Level 0 performs servo engine and mediacalibration processes 806. If the error was not sufficiently correctedat level 0, level 1 performs notch calibration process 808 and thenperforms servo engine and media calibration processes 806 using the newvalues for the notch filter. Update flash process 810 is performed atthe end of both level 0 and level 1 recalibration to update currentcalibration values, or add another set of calibrations values that maybe factored in with another set of calibration values.

[0124] Level 2 recalibration includes performing focus offset jittercalibration process 812 to correct focus problems, followed by servoengine and media calibration processes 806. Level 3 performs trackingoffset jitter calibration process 814 to correct tracking errors,followed by servo engine and media calibration processes 806. Level 4performs adjust focus loop gain process 816, and level 5 performs adjusttracking loop gain process 818. Levels 4 and 5 can include adjusting thegain to achieve a particular crossover frequency. In one implementation,the loop gain is measured by injecting a fixed frequency and amplitudeinput signal into the closed loop and measuring the amplitude of theloop's response at the same frequency. The ratio of the loop's responseover the injected amplitude is the loop gain. This technique ofadjusting loop gain can affect the stability margins of drive 100 (FIG.1a).

[0125] The servo engine calibration values include all values requiredto calibrate drive 100. The media calibration values are a subset of theservo engine calibration values, which include only those parameterswhich vary as different pieces of media are inserted into the drive. Thecalibrated values include: OPU 103 (FIG. 1a) offsets and gains, focusclosed threshold, focus sensor gain and offset, tracking sensor gain andoffset, focus loop gain, tracking loop gain, notch locations, sensorcrosstalk gain, focus sensor linearization, and tracking sensorlinearization. The media calibrations include: focus sensor gain andoffset, and tracking sensor gain and offset.

[0126] In one embodiment, the loop gain is measured by injecting a fixedfrequency and amplitude input signal into the closed loop and measuringthe amplitude of the loop's response at the same frequency. A digitalsummer is created in the DSP 304 to sum the input sinewave signal withthe output of a compensator. The output of the digital summer isconverted from a digital to an analog signal. The ratio of the output ofthe compensator over the output of the digital summer is the total openloop gain. This ratio should be 1.0 if the frequency of the disturbanceis at the desired crossover frequency and the gains are correct, asfurther described in The Servo System Calibration disclosures.

[0127] Referring again to FIG. 8, process 824 checks the value of astatus indicator returned by servo recalibration process 802. If thecalibration was successful, then process 826 monitors whether focusmisregistration (FMR), track misregistration (TMR), and read jitter arewithin predetermined limits. If FMR, TMR, and read jitter are withinlimits, then a status variable is set to indicate “no errors” in process828 and control is returned to servo thread 404 (FIG. 4). If FMR, TMR,and read jitter are not within limits, or if process 824 returns afailed status, then process 830 adjusts the recalibration level toincrease the effort to correct the problem. If all of the levelsavailable have not been attempted, then control transfers to process 802to perform the next level of recalibration. If all of the recalibrationlevels available have been attempted, then the status variable is set toindicate that an error is still present in process 832 and controltransfers back to servo thread 404.

[0128] Heartbeat Interrupt

[0129] Referring now to FIG. 9, a flow diagram of processes that can beincluded in heartbeat interrupt 408 is shown. In the embodiment shown,the time between heartbeat interrupts 408 is a variable that can be setand passed to heartbeat interrupt 408 according to a particularapplication or implementation of drive 100 (FIG. 1a). In otherembodiments, the time allowed can be fixed to a particular value.Process 902 disables further interrupts so that the interrupt lastreceived from servo thread 404 (FIG. 4) can be processed. The interruptcounter is updated by a delta time value to create a timing clock usedby the state machines that are implemented in the heartbeat interrupt408. The delta time value can be set to any increment desired, such as avalue that corresponds to the rate of the heartbeat, in process 903.Process 904 reads the DSP status register, such as shown in FIG. 3f, todetermine the status of the DSP 304 (FIG. 3).

[0130] In one embodiment, heartbeat interrupt 408 invokes a set of statemachines that manage various time-critical functions in heartbeatinterrupt 408. The embodiment shown in FIG. 9 includes power mode statemachine 910, recovery manager 912, tracking/seeking control statemachine 914, focus control state machine 916, spin control state machine918, monitor PSA state machine 920, laser control state machine 922,adjust gains state machine 924, performance monitor state machine 926,and monitor load/eject process 928. These processes are executed onceevery pass through heartbeat interrupt 408. Process 930 exits thecurrent interrupt and re-enables interrupts once the processes in theheartbeat interrupt 408 are complete.

[0131] In other implementations, other processes can be included toperform functions in addition to, or instead of, the processes shown inFIG. 9. Further, one or more of the processes can be executed atdifferent frame rates relative to other processes.

[0132] Monitor Power Mode

[0133] Processor 302 (FIG. 3) can function in different power modes suchas sleep mode (low power consumption), high power mode, and operatingmode. FIG. 10 shows one example of a state machine representingprocesses performed by power mode state machine 910 that includes arequest digital signal processor (DSP) only mode 1032, a request minimumpower mode 1034, a request idle power mode 1036, and a request fullpower mode 1038.

[0134] In the request DSP only mode 1032 and request minimum power mode1034, process 1040 determines whether any loops are open or closed. Arequest to change power modes can originate from the servo thread 404,the heartbeat interrupt 408 or any of the utility threads 414. Ideally,a power mode other than high power mode would not be requested while theservo tracking, focus or spindle loops are closed. Process 1040determines whether any servo loops are closed and coordinates openingthe loops before continuing to the requested power mode. Once all loopsare open, process 1042 disables the mailbox interrupt service routine,which is further described hereinbelow in the discussion of FIG. 21.

[0135] The power mode is then set to DSP only in the request DSP onlymode 1032, and to minimum power in the request minimum power mode 1034.Note that process 1044 continues to monitor load/eject switches in theminimum power mode 1034. Process 1048 function which is called at theend of any interrupt. When the power mode reaches DSP_ONLY, MIN_POWER orIDLE_POWER, there is no need to execute all the state machines in theheartbeat interrupt 408. To bypass the execution of these statemachines, we use the K_OS_Intrp_Exit function to end the heartbeatinterrupt after executing the Monitor Power Mode state machine.

[0136] When the power state is minimum power (MIN POWER) mode, the powerstate can transition to the idle mode. In the MIN POWER mode, the drive100 detects if a cartridge is present to be loaded or if a cartridgeeject has been requested. The power mode transitions to the idle mode toperform the load or eject operation. The monitor load/eject process 928initiates the REQUEST IDLE process 1036. Process 1046 continues tomonitor load/eject switches in the idle power mode.

[0137] When full power is requested, the request full power mode 1038re-enables the mailbox interrupt routine and sets the power to full on.

[0138] Recovery

[0139]FIG. 11 shows an overview flow diagram of functions performed byone embodiment of recovery manager 912 that can be implemented torecover from problems with focus, tracking, or spin. The current drivestate is stored in process 1104 based on parameters supplied by servothread 404, heartbeat interrupt 408, and DSP status mailbox interrupthandler 410. This allows the state of the drive 100 (FIG. 1a) to berestored to resume processing any commands at the point where they wereinterrupted when the problem was detected.

[0140] Process 1106 classifies the problem as a spin, focus, or trackingproblem based on error status information supplied by servo thread 404,heartbeat interrupt 408, and DSP status mailbox interrupt handler 410.Once the problem is classified, process 1108 finalizes the state to berestored, which may include determining the command that wasinterrupted, and storing the information where it can be accessed torestore the interrupted command.

[0141] Process 1110 performs clean up before attempting to recover fromthe problem or error detected in process 1114. The steps performedduring the cleanup process can vary depending on the state of the drive100 (FIG. 1a) when the error was detected. Such clean up can include,for example, managing laser power so that data is not written in anunintended location on the optical media 102 (FIG. 1a).

[0142] When an “off disk” condition is detected, process 1112 biases thetracking actuator arm 104 (FIG. 1a) back on to the optical media 102. Ifthe actuator arm 104 does move back on to the optical media 102, thenprocess 1114 restores the previous drive state that was interrupted whenthe error was detected.

[0143] If process 1114 cannot recover from the tracking, focus or spinerror, then failed recovery cleanup process 1116 is invoked to perform“cleanup” tasks, such as turning track and/or focus off, depending onthe problem. Process 1118 requests a RECOVERY_FAILED event from the RTOS406 (FIG. 4) to indicate that recovery was attempted, but not achieved.

[0144] If recovery was successful, process 1114 issues a notice that thedrive state was restored to process 1120, which then clears error bitsin mailboxes 306 (FIG. 4) and requests a RECOVERY_COMPLETE event fromthe RTOS 406.

[0145]FIG. 11a shows a recovery state machine 912′ that corresponds torecovery manager 912. FIG. 11a shows states 1104′-1120′ that correspondto processes 1104-1120 in FIG. 11. The criteria shown above dashed linesin FIG. 11a indicate the conditions required to transition to the nextstate, and the information below the dashed lines indicate the actiontaken upon transition.

[0146] In one embodiment, the following servo error states can beindicated by track, focus, and spin control processes:

[0147] Off Disk

[0148] Failed Auto Jump

[0149] Long Seek Failed

[0150] Failed Jump

[0151] Calibration Failure

[0152] Bad Spin

[0153] Bad Track

[0154] Bad Focus Caused Track

[0155] Bad Focus

[0156] Error Failed

[0157] Got Notify Event

[0158] Timed Out

[0159] Aborted

[0160] In one embodiment, the following recovery restore states can besaved:

[0161] Continue long seeks

[0162] Continue jumps

[0163] Reposition Current Track

[0164] Enable Auto Jumpback

[0165] Track On

[0166] Repeatable Run-Out (RRO) On

[0167] Constant Linear Velocity (CLV) Data

[0168] Spin On

[0169] Focus On

[0170] Off Disk Detection

[0171] Optical media 102 for drive 100 (FIG. 1a) can be very small andit can be difficult to prevent the OPU 103 from moving off the formattedarea of the optical media 102, such as at the innermost or outermostdiameter, where there are no tracks. FIGS. 12a-12 c show an example ofan off disk detection process 1200 for detecting an off disk condition.FIG. 12a shows a diagram of an embodiment of an off format detectionmanager that is executed as part of the classify problem state 1106′ inFIG. 11a.

[0172] In FIG. 12a, process 1202 includes detecting track crossings whenattempting to close tracking. If the DSP 304 (FIG. 3) does not detecttracking good or tracking bad within a predetermined time period, forexample, 500 milliseconds, in process 1204, an off-disk indication isset in process 1206. If the DSP 304 does detect a tracking goodcondition, process 1210 monitors the tracking control effort (TCE) todetermine whether an off disk condition exists.

[0173]FIG. 12b shows a diagram of components utilized to perform offformat detection for the off format detection manager shown in FIG. 12a.FIG. 12b shows the relationship between the TCE signal and othercomponents in drive 100, specifically, DSP tracking servo 1220 outputsthe TCE signal as a feedback signal to tracking/seeking state machine914, as well as to off disk detection process 1224. The TCE signal isbased on the track error signal. The TCE signal can be processed toindicate the level of effort being expended to achieve tracking. Amethod for generating the TCE signal is further disclosed in TheTracking and Seeking Servo System disclosures.

[0174]FIG. 12c shows a diagram of logic to perform off format detectionfor the off format detection manager shown in FIG. 12a by determiningwhether the TCE signal indicates an off disk condition. Process 1230calculates the absolute value of the TCE signal. Process 1232 includesinputting the absolute value of the TCE signal to a filter, such as alow pass filter, to remove high frequency noise. In one embodiment, thecutoff frequency of the low pass filter is 10.6 Hertz, however othercutoff frequencies can be implemented according to the dynamics andfrequencies associated with drive 100.

[0175] Monitor Tracking/Seeking Servo

[0176]FIGS. 13a-13 c show an embodiment of tracking/seeking controlstate machine 914 represented by control state diagrams 1300, 1302, 1304for monitoring and controlling track functions for drive 100 (FIG. 1a).FIG. 13a pertains to turning track on and off, FIG. 13b pertains totrack jumps, and auto jumpback, and FIG. 3c pertains to long seeks.

[0177] Referring now to FIG. 13a, when a tracking turn on servo commandis received while tracking acquisition state machine 1300 is in thetracking idle state 1306, tracking acquisition state machine 1300transitions to tracking turn on state 1308. If focus is not on, thentracking acquisition state machine 1300 enters tracking illegal state1310. If the drive has flash memory which contains valid calibrationvalues for operating over both premastered media and writeable media,the gain measure states 1380 and 1382 are used to determine whether theOPU 103 is currently over the premastered or the grooved areas, and toselect the values appropriate for the area of the media.

[0178] Before transitioning from track turn on state 1308 to gainmeasure state 1380, a nominal TES gain and offset are programmed and theDSP 304 (FIG. 3) is configured to measure the peak to peak amplitude ofthe TES signal. Gain measure state 1380 enables the DSP 304 to begin tomeasure the TES peak to peak amplitude and then transitions to gainmeasure state 1382. Gain measure state 1382 allows the DSP 304 apredetermined time period, such as 25 milliseconds, to complete the TESpeak to peak amplitude measurement. When the measurement is complete, adecision regarding media area type is made based on the resultantamplitude. A relatively small amplitude indicates that the OPU 103 iscurrently over premastered media and the values appropriate forpremastered media are loaded. A relatively large amplitude indicatesthat the OPU 103 is currently over an area of writeable media and thevalues appropriate for writeable media are loaded. Also in gain measurestate 1382, the WRITEABLEMEDIA bit (FIG. 3d) of DSP Control Register 3(FIG. 3a) is set or cleared to tell the DSP 304 what type, or area, ofmedia the OPU 103 is over, as further described in The Tracking andSeeking Servo System disclosures. The tracking acquisition state machine1300 then transitions from state gain measure state 1382 to enabletracking state 1384.

[0179] Referring back to track turn on state 1308, if the drive 100 doesnot have valid calibration values stored in flash memory, then the gainmeasure states 1380 and 1382 are not used. Instead, the tracking statemachine 1300 transitions directly from track turn on state 1308 toenable tracking state 1384. In enable tracking state 1384, a trackingacquisition process in DSP 304 is invoked as further described in TheTracking and Seeking Servo System disclosures, and tracking waitacquisition state 1312 becomes active for a predetermined time delayperiod. When the delay period expires, a tracking integrator is enabledin the tracking acquisition process, and tracking wait integrator state1314 becomes active for a predetermined delay period. When the delayperiod expires, the state transitions to the tracking wait track errorsignal (TES) integrity state 1316 for another delay period beforeentering the tracking status state 1318.

[0180] If the tracking status is track_OK, the state transitions to andremains in tracking active state 1320 until a problem with tracking isdetected, at which point the state transitions to tracking turn offstate 1322. The state then transitions through a series of tracking zerostates 1323-1324 to reset control flags and clear variables in the DSP304 (FIG. 3) associated with tracking before entering tracking off state1332.

[0181] While in the tracking active state 1320, a command to jump asingle track or multiple tracks on optical media 102 (FIG. 1a) can beissued. Track jumps can be implemented in a number of different waysincluding jumping two or more at one time, jumping one track eachrevolution of the optical media 102, and jumping a specified multiple oftracks every specified number of revolutions of optical media 102. Thejumps can be in the forward or reverse directions.

[0182] In one embodiment, laser power can be reduced to a low power modefrom a high power mode while in the tracking active state 1320 duringtrack seeking functions. The laser power mode can also be reduced to thelow power mode upon transition to the tracking turn off state 1322.

[0183]FIG. 13b shows an example of a state chart that can be implementedto control track jumps. When a single track jump command is received,the state transitions from tracking active state 1320 to begin singlejump1 state 1332, where variables are set to indicate that it is notsafe to read from or write to optical media 102 at this time. The statethen transitions to begin single jump2 state 1334, which issues a singletrack seek control command to DSP 304. When an auto jumpback command isreceived, the state transitions from tracking active state 1320 to beginauto jumpback state 1333, where variables can be set includingparameters to indicate the jump type, the number of tracks to jump, thedelay between track jumps, the number of revolutions (spin edge count)between jumps, the revolution counter (spin edge counter), and that itis not safe to read from or write to optical media 102 at this time. Thestate then transitions to sync auto jumpback state 1335, whichinitializes pertinent parameters and issues a single track seek controlcommand to DSP 304 once the pertinent spindle index occurs. If the PSAstate is not in PSA idle state 1602 (FIG. 16), then the PSA state is setto idle before entering the sync auto jumpback state 1335. The PSAstates are further described hereinbelow in the discussion of FIG. 16.

[0184] An adjust bias function 1337 can be performed to provide the lowfrequency tracking control effort (TCE) and to allow the DSP 304 tohandle the high frequency TCE.

[0185] The state then transitions to track wait jump state 1336 afterrequesting the DSP 304 to start a single track seek, the reset jumpindicator is cleared, the indicators JUMP_P1_TRACK (to indicate a jumptoward the inside diameter of the media 102) and JUMP_M1_TRACK (toindicate a jump toward the outside diameter of the media 102) are set,the track count is set, the spin edge counter is cleared, and the spinedge count is set to the track jump count. The state remains in trackwait jump state 1336 until the DSP 304 returns a status indicator ofwhether or not the seek, also referred to as track jump(s), wassuccessful.

[0186] Some status indicators that are included in the embodiment shownin FIG. 13b include: bad track status, which causes a notify andtracking event to be issued and transitions to track turn off state1322; bad jump, which causes a transition to track bad jump state 1340;and good track status, which causes a transition to track good jump1342. Note that a state change in the mailbox 306 can also cause atransition to track bad jump state 1340 or track good jump state 1342,as further explained hereinbelow in the discussion of an embodiment ofthe mailbox interrupt service routine in FIG. 20b.

[0187] The state transitions to track count jumps state 1344 aftercorresponding parameters are cleared and/or set from track bad jumpstate 1340 or track good jump state 1342. If more tracks are to bejumped, the state transitions to track jump settle state 1346, where thetransition to the track wait jump state 1336 is delayed for a specifiedtime period to allow the actuator arm 104 (FIG. 1a) time to settlebefore the next jump. If no more tracks are to be jumped and the autojump back indicator is false, the state transitions back to trackingactive state 1320. If no more tracks are to be jumped and the auto jumpback indicator is true, the state transitions back to sync auto jumpbackstate 1335.

[0188] Referring now to FIG. 13c, an embodiment of a state machine 1304for controlling long seeks in response to receiving a seek command isshown beginning with start long seek state 1350. ParametersJump_Cnt_LoB, Jump_Cnt_MidB and Jump_Cnt_HiB represent the low, middle,and high bytes of the 24 bits used by the DSP 304 to determine thenumber of tracks to seek. The adjust bias seek function 1351 can beperformed to generate a bias value for the tracking actuator arm toprovide the low frequency tracking control effort (TCE) and to allow theDSP 304 to handle the high frequency TCE. The bias before seek function1353 can be performed to store the current tracking actuator arm biasvalue before a new value for this parameter is generated in the adjustbias seek function 1351. The stored value can be used when transitioningbetween states 1352 and 1354.

[0189] Parameters such as a seek on flag, a track integrator on flag, atrack integrator reset flag, a physical sector address (PSA) idle flag,and the laser low power mode can be initialized before transitioning tolong seek gain adjust state 1358. In the long seek gain adjust state1358, the calibrated parameters appropriate for the type of media 102expected at the end of the seek are loaded. For example, if the OPU 103is expected to land on writeable media at the end of the seek, thecalibration parameters appropriate for writeable media are loaded inlong seek gain adjust state 1358. If the OPU 103 is expected to land onpremastered media at the end of the seek, the calibration parametersappropriate for premastered media are loaded in long seek adjust state1358.

[0190] The tracking control state machine 1304 then transitions to waitlong seek state 1352. If the time allotted for a seek expires before theseek is completed, or the DSP 304 has set the BAD_SEEK bit (FIG. 3g) ofthe DSP Status Register, the state transitions to failed long seek state1354. If the seek is completed, the state transitions to the long seekclear state 1356, where additional parameters can be cleared orre-initialized before transitioning to tracking wait integrator state1314.

[0191]FIG. 13c also shows an example of a head load state machine 1390.The purpose of the head load state machine 1390 is to position the OPU103 over the area of the optical media 102 containing tracks to acquiretracking. The head load state machine 1390 can be used when the drive100 is in any physical orientation or in the presence of shock and/orvibration. Orientation and/or shock and vibration could cause OPU 103 tobe positioned off the portion of the optical media 102 containingtracks.

[0192] Head load state machine 1390 can commence in a begin head loadonly state 1360 or in a begin head load state 1362. If the head loadstate machine 1390 begins in begin head load only state 1360, then thehead load state machine 1390 will complete without beginning thetracking acquisition state machine 1300. This is accomplished by settingthe fHeadLoadOnly flag to TRUE in begin head load only state 1360. Ifhead load state machine 1390 begins in the begin head load state 1362,then the head load state machine 1390 will complete and then initiatethe tracking acquisition state machine 1300. If the begin head loadstate machine 1362 detects that the focus servo loop is not closed, orthe tracking loop is closed, the state transitions track turn off state1322 where the process of shutting tracking off is initiated. In thebegin head load state 1362, if the focus servo is closed and thetracking servo is open, a bias voltage is applied to position thetracking actuator against an inside diameter (ID) crash stop in drive100. The begin head load state 1362 also sets the spindle speed to apredetermined speed, such as 2930 RPM, and programs the DSP 304 tosample and report the TES signal. Begin head load state 1362 thentransitions to headload1 state 1366.

[0193] The headload1 state 1366 delays a predetermined time period, suchas 30 milliseconds, to allow the tracking actuator time to settleagainst the ID crash stop and to give the DSP 304 time to complete thefirst measurement. The state then transitions to headload2 state 1368 inwhich more TES samples are collected. When a total predetermined numberof samples are collected, the state transitions to headload3 state 1370in which the TES samples are used to determine if the OPU 103 is overthe portion of the media 102 that includes tracks. If the OPU 103 isover the track portion, the TES has a sinusoidal shape and many of thesampled points will be away from the average value of the sine wavecloser to the peak values. When off the track portion of the OPU 103,the TES signal is not sinusoidal and is roughly centered about anaverage value except where some feature exists in the media.Consequently, if the OPU 103 is not over the track portion, most of thesampled points will be relatively close to the average value of thecollected TES samples. This difference in the scatter of the TES samplesis used in the headload3 state 1370 to determine whether the OPU 103 isover the media 102. If headload3 state 1370 determines that the OPU 103is not over the media 102, the tracking bias is reduced, thus reducingthe force pushing the tracking actuator against the ID crash stop and atransition is made back to headload1 state 1362.

[0194] This process involving states 1366, 1368 and 1370 is repeateduntil state 1370 determines that the OPU 103 is over the track portionor until the bias forcing the tracking actuator against the ID crashstop has been reduced past a predetermined point that determines thehead load state machine 1390 has failed. If the head load state machine1390 has failed, a transition is made from state 1370 to track turn offstate 1322. If headload3 state 1370 determines that the OPU 103 has beenpositioned over the track portion, the tracking bias is increased oneadditional step, in this embodiment 0×200 counts, and the statetransitions to headload4 state 1372. If the fHeadLoadOnly flag is TRUEafter a predetermined delay, such as 100 milliseconds, then a trackingevent is requested of the RTOS 406 and the state transitions to headload complete state 1376. If the fHeadLoadOnly flag is found to be FALSEafter a predetermined time delay, for example, 100 milliseconds, then atransition is made directly to the track turn on state 1308.

[0195] Monitor Focus Servo FIGS. 14a-14 c show an embodiment of focuscontrol state machines 1400, 1402, 1403, represented collectively by thefocus control state machine 916 shown in FIG. 9, for monitoring andcontrolling focus functions for drive 100 (FIG. 1a). FIG. 14a pertainsto acquiring focus, and turning focus on and off, and FIGS. 14b and 14 cpertain to determining a focus offset for ramping the actuator arm 104(FIG. 1a) away from the optical media 102 (FIG. 1a).

[0196] Referring now to FIG. 14a, when a focus servo command is receivedwhile focus control state machine 1400 is in the focus idle state 1406,focus control state machine 1400 transitions to begin focus state 1408.If the actuator arm 104 (FIG. 1a) is not ramped away from optical media102 (FIG. 1a) then the state transitions through begin ramp away state1408 to focus ramp away state 1410. Control transitions between states1410 and 1412 until the profile to ramp the actuator away from the diskhas been completed.

[0197] Once the actuator arm 104 ramps away to the determined position,the state transitions to begin focus acquire state 1414 if focus is tobe turned on. The begin focus acquire state 1414 transitions to rampfocus acquire state 1416 where it provides a focus DAC value to ramp thefocus actuator arm 104 towards the optical media until the DSP 304returns a status indicating whether or not focus closed. If the DSP 304closed focus, then focus control state machine 1400 transitions throughfocus loop closed state 1418, focus enable integrator state 1420, andfocus enable focus error signal (FES) integrity state 1422, beforeentering focus active state 1424.

[0198] If the DSP 304 issues a focus_OK status after a predetermineddelay period, then the state further transitions to focus active state1428. If the DSP issues a focus_bad status and focus is not closed, thenthe state transitions to focus push retry state 1426 and then to beginfocus state 1408 to re-attempt to acquire focus.

[0199] A method for acquiring and enabling focus that corresponds tostates 1414 through 1428, and FIG. 14b, that can be utilized in DSP 304is described in The Tracking and Seeking Servo System disclosures.

[0200] Focus control state machine 1400 can transition to focus turn offstate 1430 under the following conditions: (1) current state is the rampfocus acquire state 1416 and the maximum ramp position was reached; (2)current state is focus push retry state 1426 and best push away value isgreater than or equal to nominal/4; or (3) a focus problem developswhile in focus active state 1428. The focus turn off state 1430transitions to the begin ramp away state 1408 and focus ramp away state1410. The “best push away value” represents the control effort used whenpositioning the actuator arm 104 away from the optical media 102. Anominal push away value can be used except in the retry efforts managedby focus push state 1426. In some situations, the actuator arm 104 canbecome stuck when the push away value is too large. If attempts atclosing focus are unsuccessful, focus push retry state 1426 is enteredusing nominal/2 as the best push away value. If attempts at closingfocus are still unsuccessful, a value of nominal/4 is used as the bestpush away value.

[0201] Referring to focus ramp away state 1410, if focus is to be turnedoff, then the state transitions through a series of zero focus states toclear focus parameters in DSP 304 before issuing a focus event andentering focus away state 1432. Otherwise, if focus is not to be turnedoff, the state transitions to begin focus acquire state 1414.

[0202]FIGS. 14b and 14 c show embodiments of the focus control statemachines 1402, 1403 which can be used during calibration and engineeringtesting. States 1450 through 1454 in FIG. 14b are used to move theactuator arm 104 towards and away from the disk in a continuoussinusoidal motion. States 1456 through 1460 in FIG. 14c follow asinusoidal profile to move the actuator arm 104 from one position toanother position.

[0203] Monitor Spin Servo

[0204]FIG. 15 shows an example of a spin control state machine 918 thatcan be implemented in heartbeat interrupt 408 (FIG. 4) to monitor thespin motor 101 (FIG. 1a) for optical media 102. Spin control statemachine 918 can be implemented along with the methods for controllingthe spin motor 101 as disclosed in The Spin Motor Servo Systemdisclosures. During the start-up phase, spin control state machine 918enters spinup initialization align state 1502 and spinup align state1504 in which a rotor shaft in spin motor 101 is moved to a known stateor position to ensure that spin motor 101 is rotated in the properdirection.

[0205] When alignment is completed, the state transitions to spinupenable interrupts state 1506 to initialize various parameters. The statethen transitions to spin up complete state 1508 and to spin final checkstate 1510 to determine if the desired speed has been attained before anallotted spinup time period expires. If the spin motor 101 is spinningat the desired speed, the state transitions to spin constant linearvelocity (CLV) by track ID (also referred to as track number) state1512, where it remains until a spin problem is detected.

[0206] If the spin motor 101 did not spin up to the desired speed beforethe spinup time period expired, a spin event is issued, and the statetransitions to spin problem state 1514. Similarly, if a spin problem isdetected while in the spin CLV by track ID state 1512, a notify eventissues, and the state transitions to spin problem state 1514.

[0207] The spin problem state 1514 transitions to the spin turn offstate 1516, and then to spin braking state 1518, where it remains for aspecified time period to stop the optical media 102 from spinning. Aspin event is issued when the optical media 102 has stopped spinning,and the state then transitions to and remains in spin off state 1520until a new command to spin the media is received.

[0208] Monitor PSA

[0209]FIG. 16 shows an embodiment of a physical sector address (PSA)state machine 920 in accordance with the present invention. One uniqueaspect of optical media 102 is that it can include a pitted PSA masterarea that cannot be overwritten, and a grooved writeable area that canbe overwritten. PSA state machine 920 therefore can determine theposition of the actuator arm 104 (FIG. 1a) in relation to the groovedand pitted areas whenever tracking is Active. It is not possible to readPSAs during seeks or when tracking is not active.

[0210] If track or focus are off, PSA state machine 920 is put into thePSA idle state 1602 where no attempts to read PSAs are made. If thedrive is both focused and tracking, the PSA state machine 920 will tryto reach PSA locked state 1608 where PSAs are successfully read. Eachtime the tracking/seeking state machine 914 (FIG. 9) reaches theTRACKING ACTIVE state 1320 (FIG. 13a), it will check if the PSA state isin PSA IDLE state 1602. If so, the state transitions from PSA idle state1602 to PSA enable state 1604. Upon transitioning from PSA idle state1602 to PSA enable state 1604, the acquisition interrupts are disabledand flags are set to indicate that PSAs are not being read. Upontransitioning from PSA enable state 1604 to PSA acquiring state 1606,PSA acquisition is enabled. If the PSAs can be read, the PSA statemachine 920 transitions to PSA locked state 1608. If the ability to readis not detected within a predetermined time period, such as 48milliseconds, the PSA state machine 920 transitions to PSA RETRY state1610. PSA RETRY state 1610 toggles between settings appropriate for pitsand settings appropriate for grooves. Once the settings have beenchanged, the PSA state machine 920 begins the acquisition process againat PSA enable state 1604.

[0211] While in PSA locked state 1608, the most recently read PSA ismonitored. If a new PSA is not read before the timeout period expires,the state transitions to the PSA retry state 1610. Each time a new PSAis read, the value is compared to PSA_MAX to determine if the actuatorarm 104 is close to the last track on the optical media 102. PSA_MAXcorresponds to the last usable track on the optical media 102. If theactuator arm 104 is determined to be close to the last track, then apredetermined number of single track jumps, such as 40 single trackjumps, are commanded to move the tracking actuator arm 104 away from theedge of the optical media 102. Alternatively, a multi-track seekfunction can be used to move the tracking actuator arm 104 instead ofmultiple single track jumps. The PSA IDLE state 1602 is then commanded.Each time the PSA locked state 1608 does not have a new PSA, it predictsthe current PSA. The predicted PSA is compared to PSA_MAX to determineif the actuator arm 104 is close to the last track on the optical media102. If the actuator arm 104 is determined to be close to the lasttrack, then a number of single track jumps are performed beforetransitioning to the PSA idle state 1602.

[0212] Monitor Laser

[0213]FIG. 17 shows an embodiment of a laser control state machine 922in accordance with the present invention. The state remains in laser offstate 1702 when a laser control variable indicates that power to thelaser in OPU 103 (FIG. 1) is off. The state transitions to laser onstate 1704 when power to the laser is turned on. When the optical media102 stops spinning, the state transitions back to laser off state 1702,and a laser control variable is set to OFF. In one implementation, aspin override variable can be used to allow the laser to be turned offeven if the optical media 102 is still spinning.

[0214] Adjust Gains

[0215]FIG. 18 shows an example of adjust gains state machine 924 inaccordance with the present invention. Adjust gains state machine 924begins in gains idle state 1824, and transitions to gains adjust state1826 when tracking is active. The gains are adjusted based on thecurrent zone on optical media 102 (FIG. 1a) being accessed. In oneimplementation, optical media 102 can include sixteen different zones,and a zone calibration tables can exist for each zone. The gainscorresponding to the particular zone being accessed are loaded while thestate remains in the gains adjust state 1826. The state remains in thegains adjust state 1826 until tracking is turned off. A method forgenerating the zone calibrations tables that can be utilized with adjustgains state machine 924 is disclosed in The Servo System Calibrationdisclosures.

[0216] Monitor Performance

[0217]FIG. 19 shows an embodiment of a continuous performance monitorstate machine 926 in accordance with the present invention. In oneimplementation, performance monitor state machine 926 includes idlestate 1902, monitor initialization (init) state 1903, monitor focusmisregistration (FMR)/track misregistration (TMR) state 1904, andmonitor performance events state 1908. The state transitions from idlestate 1902 to monitor initialize state 1903 at the start ofinitialization, such as when drive 100 is powered on.

[0218] If focus and track are active, the state transitions to monitorFMR/TMR state 1904. The track and focus error signals (TES and FES) areused to generate FMR and TMR signals. If the FMR and/or TMR signalsand/or read jitter values are out of predefined limits, then the statetransitions to performance event issued state 1908 to issue performanceevents based on whether there is a problem with FMR, TMR, and/or readjitter.

[0219] Mailbox Interrupts

[0220]FIG. 20a shows a flowchart of an embodiment of DSP statusinterrupt logic 2000 that can be included in DSP status mailboxinterrupt handler 410 (FIG. 4) in accordance with the present invention.

[0221] When the DSP status interrupt occurs, process 2002 disablesfurther notification of interrupts from mailbox 306 (FIG. 4) to allowtime to process the current DSP status interrupt. Process 2004 decodesthe DSP status register to decode the message being sent by the DSP 304(FIG. 4). Examples of messages which can be sent by the DSP 304 areshown in FIGS. 3f and 3 g. In one embodiment, the messages areimplemented as status bit settings in one or more DSP control registers.Process 2004 determines which of the status bits in the DSP controlregister(s) have changed. Examples of bit settings to convey variousmessages in the DSP control register(s) are shown in FIGS. 3b, 3 c, and3 d. Specific actions are taken in processes 2006 and 2008 based onwhich status bit the DSP 304 has set. When the DSP status indicates aproblem with the operation of drive 100 (FIG. 1a), process 2006 issues arequest for a notify event, and a tracking, focus, or trace event, asrequired depending on the error condition, to RTOS 406 (FIG. 4). If themessage decoded by process 2004 indicates an error condition, thenprocess 2012 records the servo error state that is used by heartbeatinterrupt 408. Process 2008 changes focus and tracking state machinevariables based on the DSP status. At the end of the DSP statusinterrupt logic 2000, process 2010 re-enables the mailbox interrupt 306so the DSP 304 can continue to send messages to the processor 302.

[0222] Referring now to FIGS. 20a, 20 b, and 20 c, FIGS. 20b and 20 cshow an example of logic included in processes 2004-2008, which is alsoreferred to as the mailbox interrupt service routine (ISR) 2020. In FIG.20b, process 2022 decodes DSP status by determining which bits in theDSP status registers have changed from the previous pass through themailbox ISR 2020. Process 2024 then checks the TRACK_BAD andTRACK_BAD_SOURCE status variables. The status of the tracking jumps isthen tested by determining whether GOOD JUMP or BAD JUMP indicators areset in processes 2026 and 2028. If one or both of the GOOD JUMPindicators is set, process 2030 determines if the tracking state is thetrack wait jump state 1336 (FIG. 13b). If the tracking state is thetrack wait jump state 1336, then process 2032 changes the tracking stateto the track good jump state 1342 (FIG. 13b). If the BAD JUMP indicatoris set, process 2034 determines if the tracking state is the track waitjump state 1336 (FIG. 13b). If the tracking state is the track wait jumpstate 1336, then process 2036 changes the tracking state to the trackbad jump state 1340 (FIG. 13b).

[0223] Process 2038 determines whether the FOCUS_BAD indicator is set.If so, process 2040 determines if the focus state is in the focus activestate 1428 (FIG. 14a). If so, then process 2042 updates the servo errorstate indicator to indicate bad focus, process 2044 requests a notifyevent from RTOS 406, process 2046 sets the focus state to focus turn offstate 1430, and process 2048 determines whether auto jump back isenabled. If auto jump back is enabled, process 2050 update the servoerror status to indicate a failure during autojump, otherwise, process2052 determines whether the tracking state is in the track off state1332 (FIG. 13a).

[0224] If the tracking state is not in the track off state 1332, thenprocess 2054 determines whether the tracking state is in the wait longseek state 1352 (FIG. 13c). If so, process 2056 updates the servo errorstatus to indicate a failure during long seek. Process 2058 then setsthe tracking state to the track turn off state 1322, whether or not thetracking state was the wait long seek state 1352 in process 2054.Process 2060 updates the servo error status to indicate that thetracking problem was caused by loss of focus.

[0225] Process 2062 determines whether the focus state is in the focusloop closed state 1418 (FIG. 14a). If so, then process 2064 determineswhether the DSP status indicates that ramp focus has been acquired. Ifso, then process 2066 sets the focus state to the focus loop closedstate 1418.

[0226] In FIG. 20c, process 2064 decodes DSP status by determining whichbits in the DSP status registers have changed from the previous passthrough the mailbox ISR 2020. Process 2066 then checks the TRACK_BADstatus variable. If TRACK_BAD is set, process 2068 determines if thetracking state is in the process of closing tracking. If not, process2069 determines whether tracking is active. If tracking is active, thenprocess 2070 updates the servo error state to BAD_TRACK, process 2071requests a notify event from RTOS 406, and process 2072 sets the trackstate to the track turn off state.

[0227] Referring again to process 2069, if tracking is not active,process 2073 determines whether a jump (seek) is in progress. If a jumpis in progress, process 2074 updates the servo error state to BAD_TRACK,FAILED_JUMP. Process 2075 then determines whether the tracking state isin the auto jump back state. If not, then process 2076 determineswhether a command is active. If so, process 2077 issues a trackingevent. If process 2076 determines that a command is not active, thenprocess 2079 issues a notify event.

[0228] Referring again to process 2075, if the tracking state is in theauto jump back state, then process 2078 updates the servo error state toFAILED_AUTOJUMP, and process 2079 issues a notify event.

[0229] Referring again to process 2073, if a jump is not in progress,process 2080 determines whether a long seek is in progress. If so, thenthe DSP status is set to indicate LONG_SEEK_FAILED in process 2081 andprocess 2077 issues a tracking event.

[0230] Process 2072 sets the track state to the track turn off stateafter processes 2077 and 2079 are finished, or if process 2080determined that the track state was not the long seek state.

[0231] Process 2082 then determines if any other bits in the DSP statusregisters have changed from the previous pass through the mailbox ISR2020. Process 2083 checks the TRACK_BAD_SOURCE status variable is set.If TRACK_BAD_SOURCE is set, process 2084 determines if the trackingstate is in the process of closing tracking. If not, process 2085determines whether tracking is active. If tracking is active, thenprocess 2086 updates the servo error state toBAD_FOCUS_CAUSED_BAD_TRACK, process 2087 requests a notify event fromRTOS 406, and process 2088 sets the track state to the track turn offstate.

[0232] Referring again to process 2085, if tracking is not active,process 2089 determines whether a jump (seek) is in progress. If a jumpis in progress, process 2090 updates the servo error state to BAD_TRACK,FAILED_JUMP. Process 2091 then determines whether the tracking state isin the auto jump back state. If not, then process 2092 determineswhether a command is active. If so, process 2093 issues a trackingevent. If process 2092 determines that a command is not active, thenprocess 2095 issues a notify event.

[0233] Referring again to process 2091, if the tracking state is in theauto jump back state, then process 2094 updates the servo error state toFAILED_AUTOJUMP, and process 2095 issues a notify event.

[0234] Referring again to process 2089, if a jump is not in progress,process 2096 determines whether a long seek is in progress. If so, thenthe DSP status is set to indicate LONG_SEEK_FAILED in process 2097 andprocess 2093 issues a tracking event.

[0235] Process 2088 sets the track state to the track turn off stateafter processes 2093 and 2095 are finished, or if process 2096determined that the track state was not the long seek state.

[0236] The various embodiments and implementations of the servo controlsystem described herein thus address the combination of servo systemdesign challenges. The servo control system architecture includes uniquemethods of sharing a general purpose processor between the servo systemand the other drive systems, unique methods of using a dedicated highspeed processor for time critical servo functions, unique methods forcommunicating between the dedicated servo processor and the sharedgeneral purpose processor, unique methods of distributing the servoprocessing between the general purpose processor and the dedicated servoprocessor, and unique methods of distributing the servo processingwithin the general purpose processor between a main loop servo threadprocess and a background periodic heartbeat interrupt process.

[0237] The architecture addresses problems with performing operations onmedia having a small form factor, such as the need for periodicrecalibration, compensation for the flexible focus and trackingactuators, nonlinear and crosscoupled tracking and focus positionsensors, dynamic crosscoupling between the multiple servo loops, needfor low power to conserve battery life, removable and interchangeablemedia, need to handle media defects exacerbated by the first surfacerecording, presence of both premastered and user writeable areas on thesame disk, need to operate in wide range of conditions including anyphysical orientation, wide range of temperatures and humidity, and thepresence of shock and vibration.

[0238] Embodiments of the present invention can be implemented tofunction on one or more computer processors, however those skilled inthe art will appreciate that certain aspects of various embodiments canbe distributed as a program product in a variety of forms, and that thepresent invention applies equally regardless of the particular type ofsignal bearing media used to actually carry out the distribution.Examples of signal bearing media include: writeable type media such asfloppy disks and CD-ROM, transmission type media such as digital andanalog communications links, as well as media storage and distributionsystems developed in the future.

[0239] The foregoing detailed description has set forth variousembodiments of the present invention via the use of block diagrams,flowcharts, and examples. It will be understood by those within the artthat each block diagram component, flowchart step, and operations and/orcomponents illustrated by the use of examples can be implemented,individually and/or collectively, by a wide range of hardware, software,firmware, or any combination thereof.

[0240] The above description is intended to be illustrative of theinvention and should not be taken to be limiting. Other embodimentswithin the scope of the present invention are possible. Those skilled inthe art will readily implement the steps necessary to provide thestructures and the methods disclosed herein, and will understand thatthe process parameters and sequence of steps are given by way of exampleonly and can be varied to achieve the desired structure as well asmodifications that are within the scope of the invention. Variations andmodifications of the embodiments disclosed herein can be made based onthe description set forth herein, without departing from the spirit andscope of the invention as set forth in the following claims.

Appendix A

[0241] See attached CD-ROM Copy 1 and Copy 2 APPENDIX B DATE CREATEDTIME BYTES FILENAME 08/09/01 05:50 p 17,301 Defin_h.txt 08/10/01 02:13 p85,660 dservo_c.txt 08/09/01 05:47 p 33,958 dspmem_h.txt 08/09/01 05:45p 292,400 dspp_c.txt 08/09/01 05:44 p 292,400 dsp_p_c.txt 08/09/01 05:47p 4,287 engpar_h.txt 08/09/01 05:43 p 7,688 Focu_h.txt 08/09/01 05:48 p3,764 indus_h.txt 08/09/01 05:49 p 69,191 rpmtbl_h.txt 08/09/01 05:47 p96,378 scmd_c.txt 08/09/01 05:49 p 7,414 SineTb_h.txt 08/09/01 05:46 p8,819 sintrp_c.txt 08/09/01 05:45 p 327,430 smain_c.txt 08/09/01 05:50 p27,961 smain_h.txt 08/09/01 05:48 p 97,596 sspin_c.txt 08/09/01 05:46 p189,471 stint_c.txt 08/09/01 05:45 p 57,381 stools_c.txt 08/09/01 05:51p 2,185 stools_h.txt 08/09/01 05:51 p 302,470 sutil_c.txt 08/09/01 05:51p 30,265 sxtrn_h.txt 08/09/01 05:51 p 11,063 TrackC_h.txt 08/09/01 05:45p 25,479 XYram_h.txt

We claim:
 1. A system for coordinating time-critical tasks in a controlsystem for an optical disc drive for optical media with a pittedpremastered area that cannot be overwritten and a grooved user-writeablearea that can be overwritten, comprising: instructions operable tocontrol handling of a new command, a notify event, or a performanceevent comprising at least one of: a set of power mode state machineinstructions operable to control the power mode of the optical discdrive; a set of recovery manager instructions operable to attemptrecovery from an error detected while performing a command; a set offocus control state machine instructions operable to control closingfocus in the optical disc drive; a set of tracking/seeking control statemachine instructions operable to control closing track in the opticaldisc drive; a set of spin control state machine instructions operable tocontrol the spin speed of optical media in the optical disc drive; a setof physical sector address (PSA) state machine instructions operable todetermine the position of an actuator arm in relation to grooved andpitted areas in the optical media; a set of laser control state machineinstructions operable to control the power mode of a laser in theoptical disc drive; a set of adjust gains state machine instructionsoperable to adjust control system gains in the optical disc drive; a setof performance monitor state machine instructions operable to monitorthe status of the time critical tasks in the second processor; and a setof monitor load/eject state machine instructions to determine whetherthe optical media has been loaded or ejected from the optical discdrive.
 2. The system, as set forth in claim 1, further comprising: afirst processor operable to communicate with a second processor, whereinthe first processor includes: instructions operable to wait to receive anotice of at least one of: the new command being issued to the secondprocessor, the notify event, or the performance event; and instructionsoperable to control the rate at which the first processor monitors thestatus of time critical tasks in the second processor.
 3. The system, asset forth in claim 2, wherein the instructions in the first processorincrease the rate at which the first processor monitors the status ofthe time critical tasks in the second processor upon receiving the newcommand, the notify event, or the performance event.
 4. The system, asset forth in claim 2, wherein the instructions in the first processordecrease the rate at which the first processor monitors the status ofthe time critical tasks in the second processor.
 5. The system, as setforth in claim 4, wherein the instructions in the first processordecrease the rate at which the first processor monitors the status ofthe time critical tasks in the second processor once the new command,the notify event, or the performance event has been handled.
 6. Thesystem, as set forth in claim 1, wherein the power mode state machineinstructions are operable to: receive a request for at least one of thefollowing power modes: DSP only mode, minimum power mode, idle powermode, and full power mode.
 7. The system, as set forth in claim 2,wherein the power mode state machine instructions are further operableto: disable issuing an interrupt related to an error condition in thesecond processor when entering a second processor only power mode or aminimum power mode.
 8. The system, as set forth in claim 6, wherein thepower mode state machine instructions are further operable to: enableissuing an interrupt related to an error condition in the secondprocessor when entering a full power mode.
 9. The system, as set forthin claim 6, wherein the power mode state machine instructions arefurther operable to: monitor ejection or loading of a cartridge in theoptical disc drive in minimum power mode.
 10. The system, as set forthin claim 1, further comprising instructions operable to open tracking,focus, or spin servo control loops before entering a lower power mode.11. An apparatus for coordinating time-critical tasks in a controlsystem for an optical disc drive for optical media with a pittedpremastered area that cannot be overwritten and a grooved user-writeablearea that can be overwritten, comprising: means for controlling handlingof a new command, a notify event, or a performance event comprising atleast one of: means for controlling the power mode of the optical discdrive; means for attempting recovery from an error detected whileperforming a command; means for controlling closing focus in the opticaldisc drive; means for controlling closing track in the optical discdrive; means for controlling the spin speed of optical media in theoptical disc drive; means for determining the position of an actuatorarm in relation to grooved and pitted areas in the optical media; meansfor controlling the power mode of a laser in the optical disc drive;means for adjusting control system gains in the optical disc drive;means for monitoring the status of the time critical tasks in the secondprocessor; and means for determining whether the optical media has beenloaded or ejected from the optical disc drive.
 12. The apparatus, as setforth in claim 11, further comprising means for a first processor tocommunicate with a second processor, wherein the first processorincludes: means for waiting to receive a notice of at least one of: thenew command being issued to the second processor, the notify event, orthe performance event; and means for controlling the rate at which thefirst processor monitors the status of time critical tasks in the secondprocessor.
 13. The apparatus, as set forth in claim 12, wherein themeans for controlling the rate at which the first processor monitors thestatus of time critical tasks in the second processor increases the rateupon receiving the new command, the notify event, or the performanceevent.
 14. The apparatus, as set forth in claim 12, wherein the meansfor controlling the rate at which the first processor monitors thestatus of time critical tasks in the second processor decreases the rateat which the first processor monitors the status of the time criticaltasks in the second processor.
 15. The apparatus, as set forth in claim14, wherein the means for controlling the rate at which the firstprocessor monitors the status of time critical tasks in the secondprocessor de creases the rate once the new command, the notify event, orthe performance event has been handled.
 16. The apparatus, as set forthin claim 11, wherein the means for controlling the power mode of thelaser in the optical disc drive includes means for receiving a requestfor at least one of the following power modes: DSP only mode, minimumpower mode, idle power mode, and full power mode.
 17. The apparatus, asset forth in claim 12, further comprising means for controlling thepower mode of a laser in the optical disc drive include means fordisabling issuing an interrupt related to an error condition in thesecond processor when entering a second processor only power mode or aminimum power mode.
 18. The apparatus, as set forth in claim 16, whereinthe means for controlling the power mode of the laser includes enablingissuing an interrupt related to an error condition in the secondprocessor when entering a full power mode.
 19. The apparatus, as setforth in claim 16, wherein the means for controlling the power mode of alaser in the optical disc drive includes monitoring ejection or loadingof a cartridge in the optical disc drive in minimum power mode.
 20. Theapparatus, as set forth in claim 16, further comprising means foropening tracking, focus, or spin servo control loops before entering alower power mode.
 21. A method for coordinating time-critical tasks in acontrol system for an optical disc drive for optical media with a pittedpremastered area that cannot be overwritten and a grooved user-writeablearea that can be overwritten, comprising: controlling handling of a newcommand, a notify event, or a performance event comprising at least oneof: controlling the power mode of the optical disc drive; attemptingrecovery from an error detected while performing a command; controllingclosing focus in the optical disc drive; controlling closing track inthe optical disc drive; controlling the spin speed of optical media inthe optical disc drive; determining the position of an actuator arm inrelation to grooved and pitted areas in the optical media; controllingthe power mode of a laser in the optical disc drive; adjusting controlsystem gains in the optical disc drive; monitoring the status of thetime critical tasks in the second processor; and determining whether theoptical media has been loaded or ejected from the optical disc drive.22. The method, as set forth in claim 21, further comprising: waiting toreceive a notice of at least one of: the new command being issued to thesecond processor, the notify event, or the performance event; andcontrolling the rate at which the first processor monitors the status oftime critical tasks in the second processor.
 23. The method, as setforth in claim 22, wherein controlling the rate at which the firstprocessor monitors the status of time critical tasks in the secondprocessor includes increasing the rate upon receiving the new command,the notify event, or the performance event.
 24. The method, as set forthin claim 22, wherein controlling the rate at which the first processormonitors the status of time critical tasks in the second processorincludes decreasing the rate at which the first processor monitors thestatus of the time critical tasks in the second processor.
 25. Themethod, as set forth in claim 24, wherein controlling the rate at whichthe first processor monitors the status of time critical tasks in thesecond processor includes decreasing the rate once the new command, thenotify event, or the performance event has been handled.
 26. The method,as set forth in claim 21, wherein controlling the power mode of thelaser in the optical disc drive includes receiving a request for atleast one of the following power modes: DSP only mode, minimum powermode, idle power mode, and full power mode.
 27. The method, as set forthin claim 22, wherein controlling the power mode of a laser in theoptical disc drive includes disabling issuing an interrupt related to anerror condition in the second processor when entering a second processoronly power mode or a minimum power mode.
 28. The method, as set forth inclaim 26, wherein controlling the power mode of the laser includesenabling issuing an interrupt related to an error condition in thesecond processor when entering a full power mode.
 29. The method, as setforth in claim 26, wherein controlling the power mode of a laser in theoptical disc drive includes monitoring ejection or loading of acartridge in the optical disc drive in minimum power mode.
 30. Themethod, as set forth in claim 21, further comprising opening tracking,focus, or spin servo control loops before entering a lower power mode.31. A computer program product comprising: instructions to implement themethod of claim
 21. 32. A carrier wave data signal comprising:instructions to implement the method of claim 21.